The objective of this proposal is to examine the role of integrin in the process of Rous sarcoma virus induced cell transformation. Integrin is a cellular receptor for fibronectin and other extracellular matrix components and is one of the putative targets for the tyrosine kinase activity of pp60v-src. Site specific mutagenesis will be used to change the phosphorylated tyrosine and to modify the internal domain of the beta chain of integrin which includes the phosphorylated tyrosine. Vectors will be used to introduce normal and mutated beta subunit of chick integrin into Rous transformed cells, revertant cells and normal cells to access the effect of these mutants on the ability of pp60v-src to induce a transformed phenotype. The state of phosphorylation of integrin will be examined in cell membrane adhesion plaque fractions for the integrin mutants, cells transformed by different oncogenes, and during normal physiological processes. The interaction of integrin with the extracellular matrix will be manipulated by use of different substrates to determine the role of these linkages in the transformed phenotype.